mine, is dropping red hot charcoal into

liquid oxygen in a cauldron, a bowl.

You've seen it before but now we're

going to show it to like you've never

seen it.

We're going to show you how we do the

experiment from the very beginning and

we're going to show it to you with a

thermal-imaging camera so you can see

which bits get hot, which bits get cold

and even see some of the temperatures.

The first thing is that you have to

fetch some liquid nitrogen from the tank.

It's usually a bit of a chore but when you

look at the temperatures, it's really

quite interesting.

Once Neil did that he had to carry the

Dewars back to his lab, where we're going to

make the liquid oxygen. Now, liquid oxygen

has a higher boiling point than liquid

nitrogen and so you can condense liquid

oxygen using liquid nitrogen because

it's colder. So you begin with a cylinder

that's a high-pressure bottle of oxygen.

Now the pressure of the gas is far too

high to use for the experiment so you

have to reduce the pressure with a

so-called regulator which sits on the

top of the cylinder. Once you've got it

flowing you flow it through a coil of copper.

Copper conducts heat very well, so

if you put the coil of copper in the

liquid nitrogen and flow the oxygen

through, it will liquefy.

But because there's a flow it goes right

through and doesn't solidify in the coil.

So, the gas comes out of the cylinder at

a low pressure, but flowing quite fast,

it flows down a tube into the copper coil

which is cold, in the coil it liquefies

and when it liquefies the flowing gas

blows through probably droplets or slugs

of liquid out of the other side and then

it's fast enough so that it doesn't all

boil away when it goes through the last

piece of tube and then goes into a

Thermos flask. We didn't have much

oxygen, and because once it's in the bowl

it will boil away quite quickly, it was

important to get the hot charcoal ready

first. Because the charcoal will gently

burn in air so once it's hot

it can stay hot for quite a long time.

So, Neil heated the charcoal really like

lighting a barbecue.

Now, remember we only have one Thermos of

liquid oxygen and as soon as you pour

something cold into the bowl, which

starts at room temperature, a lot of it

will boil away. So, Neil didn't want to

waste the oxygen, so he cooled the bowl,

pre-cooled it with liquid nitrogen,

because he has far more liquid nitrogen

than oxygen.

The bowl's made of metal so it cools

quite quickly because it doesn't have a

very high heat capacity.

Once the bowl is cold, when he pours in

the liquid oxygen it will still boil a

little bit but it won't boil very

violently so we won't waste much.

So, in goes the liquid oxygen into the pre-cooled metal bowl.

Neil was ready, he had a container with

several pieces of hot charcoal, now

obviously when you drop them in, you have

charcoal which is carbon, which is going

to burn really brightly in the presence

of oxygen.

When it's dropped in, the ordinary video camera completely whites out,

looks really good, looks as if the

whole world has ended. But the

thermal-imaging camera looks very much

more selective wavelengths, so you can

actually see what's happening to the

piece of charcoal.

Not only can you see, but you can

measure its temperature, so you have two

really good bits of scientific information.

There was a really interesting thing

that happened, one of the pieces that

Neil dropped in went the usual flash of light.

Nobody knew what was happening, but Brady

who was looking through the thermal-imaging

camera said, it's broken in two, and then

when things had subsided, what has happened,

you could see in fact two pieces of

charcoal. It's important to stress, the

liquid oxygen is very cold, the charcoal

is very hot.

It's somewhere between 900 and a thousand

thousand degrees centigrade, and so the

way that these two can co-exist,

something that's very hot and something

that's very cold, is that the charcoal is

probably surrounded by a bubble of gas.

Now you can't see that hot gas because

it's probably not radiating in the same

way as the charcoal. But you do need to

remember you can't have a liquid at minus

nearly 200 degrees centigrade in contact

with the surface that's at a thousand

degrees centigrade. So, the charcoal

is surrounded by a cushion of air,

except it's round, so it's more like a bubble,

and that's important because of

course the oxygen gas gets much more

efficiently to the surface to maintain

the burning.

Eventually the reaction slows down and

the oxygen rushes in and cools down the

remaining fragments of charcoal.

So probably when Neil washed it out

he found some small pieces of charcoal at the bottom.

We thank Google's making and science

initiative for helping us make this video.

If you want more information about

the initiative, look down in the video description.